Modulable electric discharge lamp



Dec. 20, 1949 LEMMERS 2,491,867

MODULABLE ELECTRIC DISCHARGE LAMP Original Filed Feb. 12, 1942 5 I I il?//////////////// "1-1" I t I I I I I Inventor: EL gene Lemmers, 5 M0. 'Y

' Hi5 Afi'orneg.

Patented Dec. 20, 1.949

o STATES PATENT ornca MODULABLE ELECTRIC DISCHARGE LAMP Eugene Lemmers, Cleveland Heights, Ohio, aa-

signor to General Electric Company, a corporation of New York 3 Claims. (Cl; 176-122) This invention relates to the modulation of an electric discharge, and is especially concerned with controlling the relation between variation of the discharge current and resulting variation in the intensity of the radiation, visible or other wise, from the discharge. The invention permits of constructing a modulable discharge lamp in which the intensity or brilliance of radiation from the discharge varies-in a greater proportion than the discharge current, and, if desired, in a very large proportion. Provision can be made to adjust and vary at pleasure the proportional relation between variation of discharge current and corresponding variation of intensity of radiation. The invention is useful in connection with the translation of electrical signals derived from phenomena of almost any kind into light or other radiation, and is particularly applicable to discharge devices or lamps resembling the type known as crater lamps."

This application is a division of my copending application Serial No. 551,793, filed August 30, 1944, which issued July 20, 1948 as U. S. Patent No. 2,445,679, and which in turn is a division of my application Serial No. 430,593, filed February 12, 1942, which issued July 20, 1948 as U. S. Patout No. 2,445,678 and in which is described and claimed lamps of the positive column type, whereas the lamps specifically disclosed and claimed in this application are of the well known negative glow type.

My discharge device or lamp may comprise a cathode and a main anode spaced in front of the cathode and so arranged that the discharge between cathode and anode is visible end-on past the latter. Provision for modulating the potential difference and the total discharge current in the lamp may be made in any suitable manner, in accordance with any desired phenomenon or signal. For the purposes of my invention, another anode or control electrode may also be provided, with means for maintaining a potential difference and a resulting discharge between the cathode and this other anode. Accordingly, a part of the discharge is diverted or bled ofi from the main discharge (out of its path to the main anode) in a greater or less proportion, with the result that the end-on intensity of the radiation from the main dischar e varies in a greater proportion than does the total discharge current. One way of accomplishing this is to connect the other anode to the main anode through a resistance; and one way of varying the proportional relation between variation of the total discharge current and corresponding variation of intensity of radiation is to vary or adjust this resistance. Various arrangements and constructions may be employed, several of which will be illustrated and explained.

Still other features and advantages of the invention will appear from the following description of species and forms of embodiment, and from the drawings.

In the drawing, Fig. 1 is a fragmentary diagrammatic view of a lamp comprising my invention, together with a signal system and'sultable circuit, and Fig. 2 is a diagrammatic view of a modified form of the lamp.

Fig. 1 illustrates my invention as used in a system where signals in the form of electrical impulses of varyingintensity received from a source S are to be translated into luminous or other radiation of varying intensity which acts on, any desired receiving system or responsive means R for displaying or registering the same, here illustrated as including a focusing lens F and a photosensitive chart 0 carried by a revolving cylinder C and responsive to the light spot from the lens F. Electrical amplifying means may be interposed between the signal source S and the lamp L, being here illustrated as a vacuum tube T for producing substantially distortionless amplification. This tube T is shown connected in the usual manner to receive signals from the source S through an input circuit It and to feed the amplified output to the electrical discharge device or lamp L through an output circuit [2. A suitable D. C. source of discharge current B for the discharge device or lamp L is shown connected between the lamp cathode l5 and anode 16 through a power circuit H, the

amplifier T, and the amplifier output circuit I2.

As shown in Fig. 1, the lamp L is of the well known negative glow type comprising a glass envelope 20 enclosing the cathode [5 which consists of a hollowed cylindrical metal body with the mouth of its axial hole or bore 4|] open at one end. The main anode l6 has the form of a sheet metal cap over and around the open end of the body l5, centrally apertured in axial alignment with the hole 40 and having a flange turned toward the cathode, whil the other anode or control electrode 23 has the form of a sheet metal cylinder spaced around the body [5 and thus insulated from it, and also insulated from the anode I6. The cylinder constituting the control electrode 23 extends inside the flange of the anode structure. The anode is so arranged that the negative glow discharge in the crater is visible end-on past it. The envelope contains a suitable gaseous atmosphere, as well known in the art. The crater or anode 23 is electrically connected to the anode l8 through a connection 25, shown as including an adjustable resistance 26 located outside the envelope 20, and also a portion of the circuit i1.

In operation, the discharge current in the lamp L is proportional to the. signal intensity from S. The intensity of the endwise radiation from the discharge toward the receiving system B depends on the discharge current; In the absence of the anode means 23 with its connection 25, the'intensity of the discharge would vary in sole dependence on the discharge current. However,

the resistance 28 in the connection 25 makes the part 23 an anode of lower potential relative to the cathode i than the main anode i6, so that part of the discharg goes to this part 23, diminishing its end-on intensity of radiation. The

degree to which this takes place depends on the magnitude of the resistance 26 in the connection 25, as well as on the position of the part 23. If the eflective resistance 26 were zero, all the discharge would go to the part 23 if it were infinite, or virtually so, all the discharge would go to the main anode IS. The positive potential of the part 23 relative to the discharge within it depends, of course, on the value of the resistance 26, and can be increased by reducing this resistance, and vice versa.

Whatever the value of the resistance 26, the effect of the part 23 and the connection on the current-light curve of the device is subtractive in the sense that the light for a given dis charge current flowing in the circuit I1 is reduced. Naturally, this effect is proportionally greater for low currents, since the smaller the current flow, the greater the proportion of it that can be accommodated by the path via the part 23 and the resistance 26, which gives rise to a lower intensity of radiation than an equal current via the main anode i6. Accordingly, the lower end of the current-light curve is depressed very greatly in proportion to its height above zero, while the upper end of this curve is scarcely afiected. Thus the connection 25 with its resistance 26 makes the end-on intensity of radiation toward the receiving system It vary in a greater ratio than the discharge current, and this ratio can be altered by adjusting the resistance 26.

Fig. 2 illustrates diagrammatically a somewhat diiferent type of crater lamp of the negative glow type also embodying the invention. Here the cathode 15a consists of a hollowed cylindrical metal body enclosed in an insulative sleeve 4i with an internal flange 42 covering one end of the body |5a around the mouth of its exposed major cathode hole 40a. The mouth of a minor cathode hole 43 in the other end of the body i5a is also exposed. The main anode lea has the form 0! a sheet metal cap over and around the flanged end of the insulator 4|, centrally apertured in axial alignment with the major hole a, while the other anode 23a has the form of a sheet metal cap over and around the other end of the insulator II and cathode lid, with a central metal boss projecting into the minor hole It. The circuit connections are essentially the same as shown in Fig. 1, and are marked with the same reference characters, as a means of dispe with repetitive description.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A modulable gaseous electric discharge lamp of the negative glow type comprising a sealed en- 'velope containing an ionizable medium, a hollow cathode having an internally electron emissive bore, an annular sheet metal anodein front of ity is not visible in the same direction as that of the said anode.

2. A modulable gaseous electric discharge lamp of the negative glow type comprising a sealed envelope containing an ionizable medium, a hollow cathode having an internally electron emissive bore in its front end and a cavity in its back end, a sheet metal anode in front of said cathode and centrally apertured in axial alignment with said bore, and a sheet metal control electrode adjacent the back end of said cathode and having a central metal boss projecting into said cavity.

3. A modulable gaseous electric discharge lamp of the negative glow type comprising a sealed envelope containing an ionizable medium, a hollow cathode having an internally electron emissive bore in its front end and a cavity in its back end. an insulative sleeve on the exterior surface of said cathode, an anode in the form of a sheet metal cap over the front end of said cathode and centrally apertured in axial alignment with said bore. and a control electrode in the form of a sheet metal cap over the back end of said cathode and having a central metal boss projecting into said cavity.

EUGENE LEMMERB.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,834,251 Moore Dec. 1, 1931 1,970,223 Case Aug. 14, 1934 2,055,753 Schnitzeler Sept. 29, 1936 

